Pipe couplings that engage with the internal surface of a pipe are known. Such couplings typically comprise a body having a diameter that is slightly smaller than that of the inside diameter of a pipe to which they are adapted to couple with. The body includes gripping means and sealing means mounted to its external surface to engage with the internal surface of the pipe. The gripping means and sealing means are usually mounted in grooves formed in the body. The gripping means and sealing means project out of the grooves so they can effectively engage with the inside surface of a pipe. The gripping means and sealing means are typically adapted to project sufficiently out of the grooves to compensate for any slight deviations in the diameter of the pipe due to manufacturing tolerances, for example. Thus, when the pipe coupling is inserted into a pipe end, the sealing means is compressed as it engages with the end of the pipe and is forced into the pipe.
The most common type of sealing means used in these couplings are O-rings. O-rings are particularly effective at sealing between the coupling and the pipe. If the pipe end is not prepared appropriately it can be difficult for the sealing means to be reliably received within the pipe. This problem is exacerbated the more the seal projects from the groove to compensate for tolerances. Insufficiently prepared pipes may have burrs caused by cutting of the pipe or may not have been chamfered. Further, if the pipe has been deformed when it was cut, or squashed, or the coupling is inserted into the pipe at an angle to the pipe's axis, the sealing means can be drawn out of its groove making the seal ineffective. Thus, as the pipe coupling is inserted into the pipe, the sealing means will engage with the pipe end, which may cause the sealing means, or more commonly a part of the sealing means, to leave its groove and compromise the seal.